System and method for conditioning a toner before development

ABSTRACT

An image forming system and method of using the system includes a development station for developing an image, a replenishing source that stores toner mixed to a desired color and comprising at least two toner component colors, a conditioning station that conditions the toner before sending the toner to a developing station, and a drawing device that draws a portion of the toner in the conditioning station. The drawing device will remove a portion of at least one component color of the toner until the desired color is suitable for developing. The system and method will help to produce images of a desired color in liquid immersion development of color prints. With the use of the drawing device, consistent colored images can be achieved while reducing waste of toner.

TECHNICAL FIELD

The present invention relates generally to electrophotographic printingin image forming systems, and specifically relates to liquid immersiondevelopment of color prints.

BACKGROUND OF THE INVENTION

Electrophotographic systems employing liquid immersion development (LID)technologies are well known. These types of systems typically include animage bearing member or photoreceptor having an image bearing surface onwhich latent images are formed and developed as single color or multiplecolor toner images for eventual transfer to a receiver substrate or copysheet. Such electrophotographic systems also include a developmentstation that utilizes a liquid developer material typically having about2 percent by weight of charged, solid particulate toner material of aparticular color, that is dispersed at a desired concentration in aclear liquid carrier.

In the electrophotographic process of a LID system, the latent imagesformed on the image bearing surface of the image bearing member orphotoreceptor are developed with the charged toner particles, withexcess liquid carrier being left behind or removed such that thedeveloped images typically each contain about 12 percent by weight ofthe toner particles. The developed image or images on the image-bearingmember are then further conditioned and subsequently electrostaticallytransferred from the image-bearing surface to an intermediate transfermember. Following that, the conditioned image or images are then hot orheat transferred from the intermediate transfer member, at a heatedtransfer or transfix nip, to an output image receiver substrate or copysheet.

The ink or liquid developer material in conventional LID systems isabout 2% solids (by weight) and developed images are on the order of10%-15% solids (by weight). Such LID systems also include a biasedmetering roll for metering an amount of carrier fluid in the ink as wellas for developing images with the metered ink. Fluid metering as such,and image development, are conventionally carried out separately, andtypically by using a reverse rolling or moving metering roll.

LID systems typically also condition the initial ink developed image toprovide increased image stability by conditioning the toner before it istransferred to the development station. Such conditioning is oftenachieved in conditioning stations that are supplied toner by areplenishing source.

LID systems utilize a technology known as “pantoning.” This processdevelops images using LID Pantone® inks. By mixing fourteen Pantone®basic colors, over a thousand colors can be achieved for producinghigh-quality prints. This ability to print Pantone® colors or Pantone®inks is one of the desirable features of liquid ink electro-photography.In addition, the use of a wet instead of a dry toner in LID systemsproduces high quality prints, and is especially useful in short-runproductions where the use of some lithographic techniques are costprohibitive.

To obtain high-quality prints having a Pantone® color, the toningprocess combines development, ink application, sump management, andcontrol hardware and methodology. However, because of intrinsicproperties of the Pantone® ink, the toned color produced by thedevelopment hardware can deviate from the expected print color ifconventional toning processes are used. In particular, colors of thefinal print may not resemble those intended, resulting in poor qualityprints.

SUMMARY OF THE INVENTION

Systems and methods are described herein for implementing a toningprocess designed to minimize and stabilize color deviation on asubstrate, since conventional LID toning processes are not enough todeliver a robust product. Described below is a toning process thatincorporates a toner conditioning station, which enables robust Pantone®prints, while significantly reducing the setup time required by thetoning process.

For an effective and robust pantoning process, an ink conditioningstation is described herein. The device establishes the proper mixturefor any Pantone ink with the aid of an additional plate-out or drawingdevice and calorimeter before the ink is applied to the developmentstation.

The ink conditioning station, which is designed and optimized to providea quick setup and generate minimum waste, can be coupled withcalorimeters and feedback control to allow automatic switching betweenthe setup mode and the operational mode.

The ink conditioning station, which is designed and used in the setupmode, can also be operated in the operational mode with continuousplate-out and color monitoring. It therefore can serve the function ofon-the-fly ink conditioning to maintain the ink stability if anydisturbance occurs.

The Pantone mixture is established and maintained in the inkconditioning station. This Pantone mixture is different than the mixtureof the toned images and the replenishing Pantone mixture. In oneembodiment, the Pantone mixture can be prepared and poured into theconditioning station according to a pre-determined recipe.

The Pantone mixture, maintained in the Pantone ink replenishing source,has the same color mixture as the intent print color. The Pantonemixture is directed to the ink conditioning station. Once equilibrium isestablished and the toning process starts, little waste is generated.

The conditioned premix is manufactured along with the correspondingPantone mixture for printing, and can be provided to the customers (inrelatively small amounts) together with the given Pantone mixture. Sucha use of the premix allows an instant setup with little waste.

In particular, an image forming system for producing an image of adesired color on a substrate is described herein. The system includes aconditioning station for conditioning a toner prior to forming the imageon the substrate, and a drawing device to draw a portion of the tonerfrom the conditioning station. The system also includes a control devicecoupled to the drawing device for sending a signal to form the image onthe substrate if the drawn toner is suitable for producing the desiredcolor.

Also described herein is a method for producing an image of a desiredcolor on a substrate. The method includes filling a conditioning stationwith a toner, and drawing a portion of the toner from the conditioningstation. Subsequently, the portion of the toner is analyzed to determinewhether the toner is suitable for producing the desired color. Then,provided the toner is suitable for producing the desired color, thetoner is fed to a development station for producing the image of thedesired color on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an image forming system forproducing a desired color on a substrate, according to the teachings ofthe present invention.

FIG. 2 is a schematic representation of an intermediate station, forproducing a desired color on a substrate, of the image forming systemshown in FIG. 1, according to the teachings of the present invention.

FIGS. 3A and 3B are schematic illustrations of the operation of adrawing device during the set-up and the operational mode, according tothe teachings of the present invention.

FIG. 4 shows a flow chart indicating steps for producing an image of adesired color on a substrate, according to the teachings of the presentinvention.

FIG. 5 is a flow chart describing a method for producing an image of adesired color on a substrate, according to the teachings of the presentinvention

DETAILED DESCRIPTION OF THE INVENTION

An image forming system is provided herein that can produce coloredimages on a substrate. Image forming systems includeelectrophotographic, electrostatic or electrostatographic, ionographic,and other types of image forming or reproducing systems that are adaptedto capture and/or store image data associated with a particular object,such as a document. The system of the present invention is intended tobe implemented in a variety of environments, such as in any of theforegoing types of image forming systems, and is not limited to thespecific systems described below.

Differences in the intrinsic properties of Pantone® inks can result inpoor quality color prints. For example, differences in the toning rates,or plate-out rates, among the approximately fourteen Pantone® basiccolors, which are mixed to produce over a thousand colors, cause therelative fraction of the basic colors on a substrate, such as paper, todeviate from a desired mixture.

The difference in toning rates is mainly determined by theelectrophoretic mobility of the toner particles. LID toner particles,the pigmented resin imbedded with charge control agents (CCA), acquiretheir charges through charge exchange with the surrounding chargedirector micelles (counter ions). Pigment itself significantly affectsthe charging level and, therefore, the toner particle mobility andtoning rates. For example, Pantone® 347, a color whose hue is somewhatdark green, is a mixture of two Pantone® basic colors, “Pantone® ProcessBlue” and “Pantone® Yellow”, with a mass fraction of 62.5% and 37.5%respectively. Because of the variation in charging, the “blue” and the“yellow” particles have different mobilities and toning rates. Thus, ifPantone® 347 ink is added to a sump and fed to a standard toningstation, the out-coming color of the prints differ from the color oforiginal Pantone® 347.

The degree of deviation mostly depends on the difference in themobility. Let,

C_(i)=Concentration of Toner Species i (g/cm³)

μ_(i)=Mobility of Toner Species i (cm²/V-sec)

K_(i)=Developability Constant of Toner Species i=K

V=Sump Volume (cm³)

ψ_(i)=Ink Replenishing Rate (cm³/sec)

Then the product of K_(i), the developability constant, with themobility, μ_(i), relates the developed mass to the toner concentrationin a well replenished toning process:

Δm_(i)=K_(i)μ_(i)C_(i)   (1)

The developability constant, K_(i), of a given toner species i, isdetermined by the related process parameters, such as the localelectrostatic field, and the duration of development time. Often, onecan assume that the developability constant is constant across species,in which case the subscript can be dropped in favor of a constant Kvalid for all species. The mobility is determined by the charge of theparticle as well as other variables, such as viscosity of the carrierfluid, and size of the toner particles.

Referring to FIG. 1, an image forming system 10 for producing a desiredcolor on a substrate is shown. The image forming system 10 includes areplenishing source 12, an intermediate station 14, and a developmentstation 16.

The development station 16 transfers toner to the substrate, such aspaper, for producing an image thereon. The development station 16 canundertake various processes for forming a latent charge image, includingoptical image projecting onto a charged photoconductive belt or drum,charging a dielectric member with an electrostatic pin array or electronbeam, and charge projection from an ionographic print cartridge or froma plasma generator. Once a latent image is formed, the latent image maybe transferred to an intermediate member before final development.Alternatively, the latent image may be developed on the same member asthat on which it is formed, with different system architectures havingevolved to address different process priorities, such as cost, speed,preferred type of toning system or intended receiving substrate.

The replenishing source 12 contains a reservoir for storing toner. Thereplenishing source 12 supplies toner to the development station 16 viathe intermediate station 14. The intermediate station 14 conditions andhelps to regulate the color of the image produced on the substrate.

Referring to FIG. 2, the intermediate station 14 of the image formingsystem 10 is shown in more detail. The intermediate station 14 includesa conditioning station 18, or sump, which is coupled to a plate-out ordrawing device 20 and a control device 22.

The conditioning station 18 conditions the toner before transferring thetoner to the development station 16. Toner conditioning and feeding tothe development station 16 is commonly done gravitationally, ormechanically along with agitation to prevent agglomeration or lumping oftoner particles. Such lumping makes it difficult to develop the imageuniformly, detect the toner level, and can result in print deletions. Inaddition, a stream of gas may be used to convey the toner to differentparts of the development station 16. The stream of gas helps prevent thetoner from lumping.

The drawing device 20 draws toner from the conditioning station 18thereby shortening the time required for the toner concentrations toreach equilibrium in the development station 16, and helping to achievebetter quality prints. The control device 22 is coupled to the drawingdevice 20 and sends a signal to the development station 16 to producethe image on the substrate if the drawn toner is within an acceptablecolor range. The control device 22 can include a processor and/or memoryfor initiating electronic signals that feed toner to the developmentstation 16 once the toner drawn by the drawing device 20 is determinedto be appropriate for producing the desired color. The drawing device 20can consist of a pair of electrically conductive rollers with apotential difference across them. The potential difference creates anelectric field whose direction can cause the charged liquid tonerparticles to migrate to the upper roll as shown in FIG. 3A or 3B. Thedeposited toner is measured calorimetrically and removed by a scraperblade. The control device 22 can include a microprocessor that monitorsthe colorimeter and signals the main machine controller that the ink wassufficiently conditioned to begin image development. The microprocessoralso turns off the electric field in the drawing device when tonerremoval is not desired. In addition, the microprocessor can occasionallymonitor the state of the ink and take corrective action if thecolorimeter shows the ink to be outside of preset bounds. The drawingdevices include electrode surfaces and make use of the application of anelectric field to cause toner deposition. A pair of rotating rollsallows the use of a scraper blade for toner removal.

In particular, let R_(s), R_(p), and R_(r) represent the ratio of theconcentrations of species x and y in the conditioning station 18 orsump, the development station 16, which is also the ratio on the print,and the replenishing source 12, respectively. That is${R_{s}\left( {S\quad u\quad {mp}\quad R\quad a\quad t\quad i\quad o} \right)} = \frac{C_{x\quad s}}{C_{y\quad s}}$${R_{p}\left( {P\quad r\quad i\quad n\quad t\quad R\quad a\quad t\quad i\quad o} \right)} = \frac{C_{x\quad p}}{C_{y\quad p}}$${R_{r}\left( {R\quad e\quad p\quad l\quad e\quad n\quad i\quad s\quad h\quad i\quad n\quad g\quad R\quad a\quad t\quad i\quad o} \right)} = \frac{C_{x\quad r}}{C_{y\quad r}}$

where, for example, C_(xs) and C_(ys) are the toner concentrations ofspecies x and y, the two Pantone basic colors, in the sump. The hue ofeach Pantone® ink mixture, whether it is in the conditioning station 18or sump, on the print, or from the replenishing source 12, isessentially determined by the respective ratio defined above. The idealcase is R_(s)=R_(p)=R_(r). However, these ratios are not the same owingto the difference in mobility. From Eq. (1), the developed mass ratio onthe print is given by$\frac{\Delta \quad m_{x}}{\Delta \quad m_{x}} = {\frac{C_{x\quad p}}{C_{y\quad p}} = \frac{\mu_{x}C_{x\quad s}}{\mu_{y}C_{y\quad s}}}$

Therefore, $\begin{matrix}{R_{s} = {\frac{\mu_{y}}{\mu_{x}}R_{p}}} & (2)\end{matrix}$

Eq.(2) defines the required mixture in the sump for a desired printcolor. If the replenishing mixture is kept at the same mixture ratio asthe desired print ratio, then

R_(r)=R_(p)   (3)

After a relaxation time, the system eventually reaches equilibrium andthe sump then remains in the state described by Eq. (2). The dynamics inthe sump is governed by the following equation, which expressesconservation of mass: $\begin{matrix}{\frac{\left( {C_{x}V} \right)}{t} = {{C_{x\quad r}\psi} - {K\quad \mu_{x}C_{x}}}} & (4)\end{matrix}$

where C_(x) is the toner concentration of species x in the conditioningstation 14 or sump. The ink volume in the conditioning station 18, V,the developability, K, the mobility, μ_(x), and the concentration of thereplenishing ink, C_(xr), are all held constant and are thereforeindependent of time. A similar equation governs the time evolution ofspecies y. The solution of Eq. (4) is $\begin{matrix}{C_{x} = {{\left( {C_{x}^{0} - \frac{C_{x\quad r}\psi}{K\quad \mu_{x}}} \right){\exp \left( {{- K}\quad \mu_{x}{t/V}} \right)}} + \frac{C_{x\quad r}\psi}{K\quad \mu_{x}}}} & (5)\end{matrix}$

where C_(x) ⁰ is the initial toner concentration of species x. As thetime approaches infinity, the concentrations approach the equilibriumvalues: $\begin{matrix}{C_{x} = {\frac{C_{x\quad r}\psi}{K\quad \mu_{x}}\quad a\quad n\quad d\quad C_{y}\frac{C_{y\quad r}\psi}{K\quad \mu_{y}}}} & (6)\end{matrix}$

Therefore, combining Eqs. (3) and (6), $\begin{matrix}{R_{s} = {\frac{C_{x}}{C_{y}} = {{\frac{\mu_{y}}{\mu_{x}}R_{r}} = {\frac{\mu_{y}}{\mu_{x}}R_{p}}}}} & (7)\end{matrix}$

which gives the same relationship as stated in Eq. (2). At equilibrium,the concentrations in the conditioning station 18 or sump are given byEq. (2).

Equations (5) and (7) imply that the concentrations in the conditioningstation 18 eventually reach equilibrium, and that at equilibrium theprint color is the same as that in the replenishing source 12, providedthat a constant supply of the right Pantone® mixture is maintained, inaccordance with Equation (3).

The relaxation time, the time at which the first term in Eq. (5) isnegligible compared to the second term, is the time required for thecolor deviation to be within specifications. Before equilibrium isreached, prints produced by the development station 16 may not haveacceptable colors, and are typically discarded by the user of the imageforming system 10. The relaxation time, V/Kμ, indicates that the smallerthe sump or the larger the developability and toner mobility, theshorter the time required to achieve relaxation.

Referring to FIGS. 3A and 3B, a schematic illustrating the operation ofthe drawing device 20 during the set-up and the operational modes isshown. A colorimeter 24 is coupled to the drawing device 20 and to thecontrol device 22. A feed tube 26 transfers toner from the conditioningstation 18 to the development station 16.

The Pantone replenishing station 12 contains, and is replenished with,the desired Pantone ink mixture whose color becomes the print color onthe substrate. The replenishing station 12 is connected to theconditioning station 18, which directly supplies the ink to thedevelopment station 16 for the final toning of the latent images. Theconditioning station 18 serves the purpose of conditioning the Pantonemixture, in the setup mode shown in FIG. 3A, so the right ratio or colorcan be established before the ink is applied to the development station16. After the initial setup mode shown in FIG. 3a, the preferredoperational mode shown in FIG. 3B is established. In the operationalmode shown in FIG. 3B, the sump concentration ratio, R_(s), ismaintained at the level defined in Eqs. (2) and (3), relative to thereplenishing ratio, R_(r) and the identical print ratio, R_(p).

The conditioning is accomplished with the use of a drawing device 20,e.g., a pair of rotational rollers 28A and 28B, or other electrostaticdevelopment device. This device is distinct from the development station16 where the final prints are generated. In the setup mode shown in FIG.3A, a portion of the original Pantone mixture is developed to one roller28A of the drawing device 20 and discarded, and the remaining ink,carried by the other roller 28B, is fed back to the conditioning station18, or sump. Since the sump volume, V, is relatively small, theequilibrium and the right mixture ratio is established rather quickly. Acalorimeter 24 is used to monitor the plate-out color on the roller 28A.Only when the color plated out matches well with the intended printcolor, the setup mode shown in FIG. 3A is considered finished. Then, the“conditioned ink” in the ink conditioning station 18 can be furtherdirected to the development station 16 for the final toning in theoperational mode shown in FIG. 3B. The setup mode can be enhanced byoperating the drawing device 20 so that the developability is maximized.For example, a high field, high speed process combining with a widedevelopment area (e.g., long rollers) can be used. This has the effectof shortening the setup time, V/Kμ, by reducing the sump volume, V. andincreasing the developability, K. In addition, the ink conditioningstation 18 can then be run in a continuous fashion during the printingprocess to continuously monitor and correct the conditioning sumpconcentration if required. This continuous monitoring is done at areduced developability to conserve toner.

As an illustrative example, suppose a customer color “green” is bestmatched by the Pantone mixture 347, which is placed in the Pantone inkcontainer. Pantone 347 is made of the mixture of “Pantone Process Blue”and “Pantone Yellow” with a mass fraction of 62.5% and 37.5%respectively, that is, R_(p), and R_(r) are 1.67. Suppose further thatthe “Pantone Process Blue” toner mobility is twice as high as the“Pantone Yellow” mobility. Therefore, according to (2), Rs should bemaintained at 0.83. In other words, more “Pantone Yellow” than the“Pantone Process Blue” is required in the conditioning station 16,opposite to the composition of Pantone 347 prescribed by conventionaltechniques. During the setup mode shown in FIG. 3A that utilizes thedrawing device 20, the excessive “Pantone Process Blue” is plated outand removed, while the remaining ink with higher content of the “PantoneYellow” is fed back to the conditioning station 18.

During this setup process, the color in the conditioning sump willchange and eventually turn into a fixed color, indicating thatequilibrium has been established. The color of the plate-out ismonitored constantly, which enables an automatic switch from the setupmode of FIG. 3A to the regular operational mode of FIG. 3B soon afterequilibrium is reached. An additional colorimeter can be used to measurethe color of the toned image during the regular operational mode, andthe conditioning station 18 can be re-activated if a growing colordeviation is sensed from the prints.

An apparatus that is similar to the conditioning station 18 can also beused as an individual device to determine the right “conditionedmixture” for any given Pantone color that meets the customer colorrequirement. That is, in addition to a specific Pantone ink thatcustomers require, a separated batch of “conditioned ink,” or“conditioned premix,” automatically determined by such an apparatus, canbe separately manufactured and provided to customers as well. Such aconditioned premix is poured into the conditioning station 18 in thecustomer's pantoning printers, resulting in minimum or no waste duringthe setup mode.

Once equilibrium is established and the toning process starts, littlewaste is generated. In conventional methods, the first severalsubstrates are typically discarded because the image does not have thedesired color. The present invention obviates the need to discard thefirst several substrates because after the set up mode is completed, aprocess that does not involve the discarding of substrates, the desiredcolor is maintained in the images on the substrate. Moreover, accordingto the principles of the present invention, the set up mode, in whichequilibrium is established, can be completed expeditiously by decreasingthe relaxation time V/Kμ. Thus, the fast plate-out rate and the smallconditioner sump volume described above result in quick setup and littlewaste generation compared to conventional ink conditioning methods.

Referring to FIG. 4, a flow chart is presented describing a method forproducing an image of a desired color on a substrate. In step 50, aconditioning station 18 is filled with a toner. In step 52, a portion ofthe toner is drawn from the conditioning station 18 with the use of adrawing device 20. Next, in step 54, the portion of the toner isanalyzed to determine whether the toner is suitable for producing thedesired color. A drawing device 20 having a first roller together with acolorimeter 24 can be used for this purpose. In particular, a sample ofthe portion of toner drawn by the drawing device 20 can be developed tothe first roller, and its color measured by the calorimeter. In step 56,provided the toner is suitable for producing the desired color, thetoner is fed to a development station 16 for producing the image of thedesired color on the substrate.

Referring to FIG. 5, a flow chart is presented describing a method forproducing an image of a desired color on a substrate. The toner solutioncontains a first solution of a first species and a second solution of asecond species, the ratio of the first solution to the second solutionbeing R_(p). In step 60, a conditioning station 18 is filled with a sumptoner solution containing the first colored solution and the secondcolored solution. In step 62, the sump solution is fed to a developmentstation 16 for forming the image on the substrate, wherein the ratio ofthe first colored solution to the second colored solution in the sumptoner solution is substantially (μ₂/μ₁) R_(p). Here, μ₁ and μ₂ aremobilities of the first species and the second species, respectively.

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments and methods described herein. Such equivalents are intendedto be encompassed by the scope of the following claims.

What is claimed:
 1. An image forming system for producing an image of adesired color on a substrate, the system comprising: a replenishingsource that stores toner mixed to obtain the desired color, the mixedtoner comprising at least two component colors; a conditioning stationthat conditions a toner prior to forming the image on the substrate; adrawing device that draws a portion of the toner from the conditioningstation, the drawing device removing a portion of at least one componentcolor until the toner is suitable for producing the desired color; acontrol device, coupled to the drawing device, that sends a signal toform the image on the substrate once the drawn toner is suitable forproducing the desired color.
 2. The system of claim 1, furthercomprising a development station that transfers toner to the substrate,wherein the development station and the drawing device are connected inparallel to the conditioning station.
 3. The system of claim 1, furthercomprising a colorimeter useable to test a color derived from theportion of the toner drawn from the conditioning station by the drawingdevice.
 4. The system of claim 1, wherein the drawing device includes atleast one rotational roller usable to draw the portion of the at leastone component color to be removed from the conditioning station.
 5. Thesystem of claim 1, wherein the drawing device includes a first rollerand a second roller such that a portion of the at least one componentcolor to be removed is developed using the first roller, and a portionof at least one of the remaining component colors is returned to theconditioning station by the second roller.
 6. A method for producing animage of a desired color on a substrate, the method comprising: fillinga replenishing station with a toner mixed to obtain the desired color,the mixed toner comprising at least two component colors; directing aportion of the mixed toner from the replenishing station to aconditioning station; drawing a portion of the mixed toner from theconditioning station; analyzing the drawn portion of the mixed toner todetermine whether the toner is suitable for producing the desired color;adjusting a mixture of the mixed toner in the conditioning station byremoving a portion of at least one of the at least two component colors;feeding the toner to a development station when the toner is suitablefor producing the desired color; and producing the image of the desiredcolor on the substrate.
 7. The method of claim 6, further comprising thestep of ceasing to draw the portion of the mixed toner prior to feedingthe toner to the development station.
 8. The method of claim 6, whereindrawing the portion of the mixed toner comprises drawing the portion ofthe mixed toner continuously as the image of the desired color is beingproduced on the substrate.
 9. The method of claim 6, wherein filling thereplenishing station further comprises maintaining a volume of the tonerin the replenishing station substantially constant.
 10. The method ofclaim 6, wherein, analyzing the drawn portion comprises determining acolor derived from the withdrawn portion of the mixed toner with acolorimeter.
 11. The method of claim 6, further comprising developing athe drawn portion of the mixed toner with a first roller to determinethe color of the developed portion.
 12. The method of claim 6, furthercomprising returning a fraction of the drawn portion of the mixed tonerto the conditioning station using a second roller, the returned portionhaving a different amount of at least one of the at least two componentcolors compared with the developed portion.
 13. A method of forming animage of a desired color on a substrate utilizing a toner solution ofthe desired color containing a first solution of a first species and asecond solution of a second species, the ratio of the first solution tothe second solution being Rp, the method comprising: mixing a tonersolution in a conditioning station, the toner solution containing thefirst solution and the second solution; drawing a portion of the tonersolution out of the conditioning station; removing a first fraction ofthe drawn portion; returning a second fraction of the drawn portion tothe conditioning station, the second fraction having a ratiosubstantially different from Rp, until the ratio of the first solutionand the second solution drawn out of the conditioning station issubstantially the same as Rp; and feeding the toner solution to adevelopment station to form the image on the substrate.
 14. The methodof claim 13, further comprising: analyzing the portion of the tonersolution to determine whether the toner solution is appropriate toobtain the desired color; feeding the toner to a development stationwhen the toner solution is appropriate to obtain the desired color; andproducing the image of the desired color on the substrate.
 15. Themethod of claim 14, wherein analyzing the portion of the toner solutioncomprises using a first roller to develop the first fraction of theportion of the toner solution to determine whether the toner solution isappropriate to obtain the desired color.
 16. The method of claim 15,wherein, returning the second fraction comprises using a second rollerto return the second fraction of the portion to the conditioningstation.
 17. The method of claim 15, wherein analyzing the portion ofthe toner solution comprises using a colorimeter to determine a colorderivable from the first fraction.